What is the PX25-EmissionLabs vacuum tube?

The PX25-EmissionLabs (PX25 EML) is a triode vacuum tube designed for power (set) applications. Enhanced PX25..

What is a PX25-EmissionLabs substitute or equivalent?

Direct equivalents to the PX25-EmissionLabs include PX25. These share the same pinout and operating envelope, so they can usually be swapped without circuit changes — though batch-to-batch variations between manufacturers (NOS vs current production) may shift the sonic character noticeably.

What are the key specifications of the PX25-EmissionLabs?

Amplification factor μ ≈ 10, transconductance gm ≈ 8 mA/V, plate resistance rp ≈ 1.3 kΩ, max plate voltage 400 V, max plate dissipation 25 W, heater 4 V / 2 A.

Is the PX25-EmissionLabs still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the PX25-EmissionLabs as Sought-after availability. NOS (new-old-stock) examples from RCA, Mullard, Tung-Sol, GE, Sylvania and Telefunken trade among collectors; modern production where it exists comes mostly from JJ Electronic, Electro-Harmonix, Tung-Sol (New Sensor), Genalex, and a handful of small-batch makers.

What does the PX25-EmissionLabs sound like?

Enhanced PX25.. Sonic character also depends heavily on the circuit operating point, the surrounding tubes in the stage, and the output transformer when present — use the interactive loadline calculator on this page to explore the trade-offs.

PX25-EmissionLabs PX25 EML Triode Vacuum Tube

Also known as PX25

Power triode delivering 25W for push-pull and SET designs

TriodeHeater 4 V · 2 AUX-4Emission Labs 2005

Plate dissipation: 25W
Max plate voltage: 400V
Transconductance: 8mA/V

PX25-EmissionLabs

Characteristics

Datasheet values, once each. Every value cites its sheet.

HeaterDirectly heated

Specifications of PX25-EmissionLabs — Heater
Heater voltageVh	4 V
Heater currentIh	2 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of PX25-EmissionLabs — Limiting values
Plate voltageVa max	400 V
Plate dissipationPa max	25 W

Mechanical

Specifications of PX25-EmissionLabs — Mechanical
Base	UX-4
Rarity	Sought-after
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of PX25-EmissionLabs — Small signal
Transconductance	8 mA/V
Plate resistance	1.3 kΩ
Amplification factor	10

Capacitances

Specifications of PX25-EmissionLabs — Capacitances
Grid–cathode	11.4 pF
Grid–plate	14.8 pF
Plate–cathode	8.3 pF

Charactereditorial reading, not a measurement

Specifications of PX25-EmissionLabs — Character
Gain	10%
Power	63%
Drive	99%
Linearity	95%

datasheet cited · model or editorial reading · catalogue value, no citation attached yet · nothing invented

Using this tube

Applications

SET output
Push-pull output
Headphone output

Generic triode power (set) stage

Hi-Fi stereoHeadphone amp

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : Emission Labs design notes (EML-12B-20A-20B-30A) · external audit feedbackActive model : Norman Koren

Manufacturer datasheets

2 manufacturer datasheets cross-checked for PX25 EML2 verified

PX25-EmissionLabs DatasheetFrank's Electron Tube Pages · PDF

SPICE models

Revision and verification status

Source: Emission Labs design notes (EML-12B-20A-20B-30A) · external audit feedback
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Norman Koren

Context

The PX25-EmissionLabs is a directly-heated triode from Emission Labs, introduced around 2005. It provides a gain factor (μ) of 10 with 1265Ω plate resistance. Commonly used in power (set) applications. Enhanced PX25.

History

Introduced: 2005
Manufacturer: Emission Labs
Era: Modern

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